These are questions that require some deep thinking.
“all a being is made up of are the 5 khandhas” may give a wrong impression.
Five khanadhas include EVERYTHING one has gone through from a beginning-less time.
They are almost all our memories AND future plans.
This is emphasized in the post, “Pancakkhandha or Five Aggregates – A Misinterpreted Concept“.
– For example, rupakkhandha consists of 11 types of rupa: “Eleven types of rupa (mental impressions) are in the rupakkhandha: past, present, future, near, far, fine (sukuma), coarse (olarika), likes (panita), dislikes (appanita), internal (ajjhatta), and external (bahiddha)”.
– Need to think about the above statement, “all a being is made up of are the 5 khandhas” with that in mind.
You wrote: “There is one instance in the suttas, in the Jataka, where the Buddha is greeted by a brahmin and later by his wife with ‘ Where have you been, my son, all this time’ ? The Buddha later showed the connection : they had been His parents for 500 successive human births..”
Yes. Those are the past pancakkhandha (memories about past rupa, vedana, sanna, sankhara, vinnana).
You wrote: “Where in the being are these memories ‘lodged’?”
They are in the “nama loka”, which is accessible by the mana indriya (i.e., recalling past memories).
– This is similar to using the five physical senses (cakkhu indriya, etc) to see, hear, etc of rupa in the “rupa loka”.
– More information at: “Our Two Worlds : Material and Mental”
This requires some extended thinking. I suggest to read those posts and ask more questions if needed. As I said, not many people have grasped these deeper points.
If one really needs to get a good handle, one should read “The Five Aggregates (Pancakkhandha)”
-I have not had a chance to review those posts recently. This may be a good time to for an discussion.